In recent years, a short-range and low-power radio system realizing a body area network (BAN: Body Area Network) and a sensor network (WSN: Wireless Sensor Networks) have been gaining attention.
Note that, the BAN is a short-range radio network, and for example, which realizes data exchanging within a range of about several meters between a human body and its surroundings. By using this BAN, for example, to attach a large number of brain wave sensors (EEG: Electroencephalography electrodes) on a human head, to perform brain wave monitor of large amounts of data from their brain wave sensors by wireless transmission, or wireless transmission of image data output from a capsule endoscopy medical.
Further, WSN is, for example, interspersed with a plurality of sensor terminals, and those sensor terminals are connected each other by a wireless network, and is considered to be applied to various fields.
The short-range wireless standard that realizes the above described BAN and WSN is, for example, proposed various ones, such as IEEE802.15.6 and ZigBee (registered trademark).
As described above, in a transmitter conforming to the short-range wireless standard such as IEEE802.15.6 and ZigBee (registered trademark), for example, it is difficult to achieve high data transfer rates required for applications such as EEG monitor or image transfer.
Therefore, the wireless communication apparatus includes a unique high-speed mode (high-speed data transfer mode) in addition to the standard data transfer mode, and the user may select and use a preferable data transfer modes by switching software manner.
Note that, when realizing a high-speed mode by bundling a plurality of channels, the strength of electromagnetic wave radiated from an antenna should be limited by the provision of low-power radio regulations, and thus the maximum transmit power may be limited about 30 dB to 40 dB lower than the standard power. Therefore, it is preferable for the transmitter to realize both transmission power of −10 dBm and −50 dBm depending on operating modes.
In general, the specified low-power radio equipment may be realized by inserting a fixed attenuator to an outside of a semiconductor integrated circuit (LSI chip) or by shifting a matching between an antenna and the LSI chip, and to achieve an ultra-low transmission power such as −50 dBm. However, in this method, for example, it is difficult to be used by switching the transmission power of both −10 dBm and −50 dBm.
Conventionally, as a wireless communication technology capable of switching between different transmission power modes, various proposals have been made.
Patent Document 1: Japanese Laid-open Patent Publication No. 2010-141758